Apart from the looting and unrest that shook the city over the weekend came a barrage of violence that had been all too familiar: At least 31 people were shot over three days, including eight killed.

The shootings erupted across the city, from Southwest Philadelphia to East Germantown to Mantua and West Philadelphia. Four people were shot in one spot, three in another, two in a third. The victims ranged from age 12 to 52. According to police statistics, there have been 158 homicide victims in the city as of Sunday night, a 21% increase from the same period last year.

At a news conference Monday, Mayor Jim Kenney said Philadelphia is “in the middle of one of the biggest crises in the city’s history.”

“I’m worried about everything. I’m worried about people’s safety. I haven’t slept much, to tell you the truth,” Kenney said. “We’re worried about everything.”

All of the killings occurred in a 13-hour time span from late Sunday morning to early Monday.

Around 11:40 a.m. Sunday, police said, a 23-year-old woman and two 25-year-old men were shot on the 3900 block of Fairmount Avenue in Mantua. The woman and one of the men died. The second man was hospitalized in critical condition.

About three hours later, a 30-year-old man was fatally shot during a domestic altercation while in a parking lot on the 200 block of West Oxford Street in North Philadelphia. Police said an arrest was made and a gun recovered.

Eighty minutes later, 30-year-old Chris Odom was shot four times at 26th Street and Lehigh Avenue in North Philadelphia. Odom, of nearby West Sterner Street, was pronounced dead shortly afterward at Temple University Hospital.

Then came the quadruple shooting, about 5 p.m. Sunday on the 700 block of East Clearfield Street. Police said an argument between a woman and people inside a vehicle may have sparked the gunfire. The victims included a 12-year-old boy, a 21-year-old woman, a 26-year-old man, and a 52-year old man. None was killed, each was hospitalized for treatment.

Around 8 p.m., officers responded to a shooting on 49th Street just north of Market in West Philadelphia and found Dequan Collins, 22, lying facedown, shot 15 times. Collins, of East Mount Airy, was pronounced dead soon after.

A little more than two hours later, officers responded to reports of a shooting on the 2800 block of Island Avenue in Southwest Philadelphia and found a man inside the front-passenger seat of a Honda Accord with a gunshot wound to his head. The victim, Maurice Sorzano, 19, of Sharon Hill in Delaware County, was pronounced dead at the scene. Another victim, a 22-year-old man, was injured, police said.

As Sunday eased into Monday, two more victims were added to the list. A 34-year-old man was shot four times while on the 6300 block of Musgrave Street in East Germantown early Monday. He died soon after at Albert Einstein Medical Center.

Also early Monday, two teens, one 18 and the other 17, were shot as they walked along the 100 block of North Hobart Street. The older teen was taken by police to Penn Presbyterian Medical Center, where he died.

Staff writer Justine McDaniel contributed to this article.